http://www.cchem.berkeley.edu/schaffer//2012%20Publications/Publication%20number%204.pdf

The AAV Vector Toolkit: Poised at the Clinical Crossroads

Recombinant adeno-associated viral (rAAV) vectors have shown early promise in clinical trials. The therapeutic transgene cassette can be packaged in different AAV capsid pseudotypes, each having a unique transduction profile. At present, rAAV capsid serotype selection for a specific clinical trial is based on effectiveness in animal models. However, preclinical animal studies are not always predictive of human outcome. Here, in an attempt to further our understanding of these discrepancies, we used a chimaeric human-murine liver model to compare directly the relative efficiency of rAAV transduction in human versus mouse hepatocytes in vivo. As predicted from preclinical and clinical studies, rAAV2 vectors functionally transduced mouse and human hepatocytes at equivalent but relatively low levels. However, rAAV8 vectors, which are very effective in many animal models, transduced human hepatocytes rather poorly-approximately 20 times less efficiently than mouse hepatocytes. In light of the limitations of the rAAV vectors currently used in clinical studies, we used the same murine chimaeric liver model to perform serial selection using a human-specific replication-competent viral library composed of DNA-shuffled AAV capsids. One chimaeric capsid composed of five different parental AAV capsids was found to transduce human primary hepatocytes at high efficiency in vitro and in vivo, and provided species-selected transduction in primary liver, cultured cells and a hepatocellular carcinoma xenograft model. This vector is an ideal clinical candidate and a reagent for gene modification of human xenotransplants in mouse models of human diseases. More importantly, our results suggest that humanized murine models may represent a more precise approach for both selecting and evaluating clinically relevant rAAV serotypes for gene therapeutic applications.

/pdf/selection-and-evaluation-of-clinically-relevant-aav-variants-3zdx30pjdq.pdf

Selection and evaluation of clinically relevant AAV variants in a xenograft liver model

Adeno-associated viral (AAV) vectors are a rapidly emerging gene therapy platform for the treatment of neurological diseases. In preclinical studies, transgenes encoding therapeutic proteins, microRNAs, antibodies or gene-editing machinery have been successfully delivered to the central nervous system with natural or engineered viral capsids via various routes of administration. Importantly, initial clinical studies have demonstrated encouraging safety and efficacy in diseases such as Parkinson disease and spinal muscular atrophy, as well as durability of transgene expression. Here, we discuss key considerations and challenges in the future design and development of therapeutic AAV vectors, highlighting the most promising targets and recent clinical advances.

Gene therapy for neurological disorders: progress and prospects

In vivo tissue-tropism of adeno-associated viral vectors.

Recombinant adeno-associated viral vectors (rAAVs) have been widely used for gene delivery in animal models, and are currently evaluated for human gene therapy after successful clinical trials in the treatment of inherited, degenerative or acquired diseases, such as Leber congenital amaurosis, Parkinson disease or heart failure. However, limitations in vector tropism, such as limited tissue specificity and insufficient transduction efficiencies of particular tissues and cell types, still preclude therapeutic applications in certain tissues. Wild-type adeno-associated viruses (AAVs) are defective viruses that require the presence of a helper virus to complete their life cycle. On the one hand, this unique property makes AAV vectors one of the safest available viral vectors for gene delivery. On the other, it also represents a potential obstacle because rAAV vectors have to overcome several biological barriers in the absence of a helper virus to transduce successfully a cell. Consequently, a better understanding of the cellular roadblocks that limit rAAV gene delivery is crucial and, during the last 15 years, numerous studies resulted in an expanding body of knowledge of the intracellular trafficking pathways of rAAV vectors. This review describes our current understanding of the mechanisms involved in rAAV attachment to target cells, endocytosis, intracellular trafficking, capsid processing, nuclear import and genome release with an emphasis on the most recent discoveries in the field and the emerging strategies used to improve the efficiency of AAV-derived vectors.

Intracellular transport of recombinant adeno-associated virus vectors.

Adeno-associated viruses (AAVs) use a variety of cellular receptors/coreceptors to gain entry into cells. A number of AAV serotypes are now available, and the cognate receptors/coreceptors for only a handful of those have been identified thus far. Of the 10 commonly used AAV serotypes, AAV3 is by far the least efficient in transducing cells in general. However, in our more recent studies, we observed that AAV3 vectors transduced human liver cancer cells remarkably well, which led to the hypothesis that AAV3 uses hepatocyte growth factor receptor (HGFR) as a cellular coreceptor for viral entry. AAV3 infection of human liver cancer cell lines was strongly inhibited by hepatocyte growth factor, HGFR-specific small interfering RNA, and anti-HGFR antibody, which corroborated this hypothesis. However, AAV3 vectors failed to transduce murine hepatocytes, both in vitro and in vivo, suggesting that AAV3 specifically uses human HGFR, but not murine HGFR, as a cellular coreceptor for transduction. AAV3 may prove to be a useful vector for targeting human liver cancers for the potential gene therapy.

/pdf/human-hepatocyte-growth-factor-receptor-is-a-cellular-4fo0d4s8do.pdf

Jasmine K. Kalsi

Papers

Human hepatocyte growth factor receptor is a cellular coreceptor for adeno-associated virus serotype 3